It is known to employ rotary presses for the manufacture of tablets and similar compacts. The presses have a rotor which is rotatably supported and driven about a vertical axis wherein the rotor that has a die-plate and ram guides for upper and lower rams. Those upper and lower rams are guided by appropriate control cams and at least one compression station has disposed therein an upper and a lower pressing roller or compression roller by means of which the compression rams compact the material to be compressed which is inside the dies.
Some materials to be compacted tend to adhere to the pressing surface of the upper rams after the compression procedure when the upper ram starts its return travel. The result of this effect is that the surface of the compact is not of the quality desired and, moreover, has an adverse impact on the succeeding compressing procedure. It has become known from EP 0 448 190 B1 or DE 88 16 064 U1 to mount the rams rotatably in the ram guides and set them into rotation during the return travel after a compression procedure. Rotating the rams helps eliminate the adhesion effect to a large extent. It has been known from DE 100 24 340 C2 to mount a ram insert rotatably within the ram shank, the insert having a lug which is guided in a helical line between two axially spaced lugs. The insert is loaded by a spring away from the ram shank in a downward direction.
During the return travel of the upper rams, a relief of the load takes place during which the upper ram normally is within the die. If the compact is not circular, e.g. is square-shaped, a rotation of the compression rams or inserts will not be performed.
It is the object of the invention to provide a method for operating a rotary press which makes it possible to remove the compacts with no compact material sticking thereto regardless of the cross-sectional shape of the dies.